Circular stapling device with buttress

ABSTRACT

The cartridge assembly includes a housing, a pusher member, a fastener cartridge body, a circular cartridge buttress member, and a retaining ring member. The pusher member is supported within the housing and movable between a first position and a second position. The fastener cartridge body is supported on the housing and has a tissue engaging surface that extends to an annular edge. One or both of the housing and the fastener cartridge body define an annular containment groove. The circular cartridge buttress member has a body portion and an extension portion. The body portion is supported on the tissue engaging surface of the fastener cartridge body. The extension portion extends from the body portion and over the annular edge of the tissue engaging surface. The retaining ring member is secured within the containment groove to releasably secure the extension portion of the circular cartridge buttress member to the cartridge assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/343,317, filed Nov. 4, 2016, which is a continuation of U.S. patent application Ser. No. 14/156,713, filed Jan. 16, 2014, now U.S. Pat. No. 9,504,470, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/768,661, filed Feb. 25, 2013, the entire disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to surgical stapling devices and, more particularly, to structures and methods for removably attaching buttress material to circular surgical stapling devices for use in anastomosis procedures.

BACKGROUND

Fasteners have traditionally been used to replace suturing when joining various body structures such as, for example, the bowel or bronchus. Surgical stapling devices employed to apply these fasteners are generally designed to simultaneously cut and seal tissue to reduce the time and risks involved with anastomosis procedures.

Circular surgical stapling devices are employed by surgeons to sequentially or simultaneously apply one or more surgical fasteners, e.g., staples or two-part fasteners, to body tissue for the purpose of joining segments of body tissue together and/or for the creation of anastomoses. Circular surgical stapling devices generally include an annular fastener cartridge assembly that supports a plurality of annular rows of fasteners, an annular anvil assembly operatively associated with the fastener cartridge assembly which provides a surface against which the fasteners are formed upon a firing of the circular stapling device, and an annular blade for cutting tissue.

For most procedures, the use of bare fasteners, with the fasteners in direct contact with the patient's tissue, is generally acceptable. The integrity of the tissue will normally serve to prevent the fasteners from tearing out of the tissue and compromising the sealing before healing has occurred. However, in some surgical operations buttress materials are employed by surgeons in combination with circular stapling devices to bridge, repair and/or reinforce tissue defects within a patient. In particular, buttress materials reduce the trauma suffered by the patient, reduce the instances of leakage, reduce the instances of bleeding, and create a relatively strong bond between adjacent body tissues.

Accordingly, there is a need for reliably and removably attaching buttress material onto a circular stapling device so that the buttress material does not interfere with the operation of the device, remains on the device until after the fasteners are fired, and is convenient and easy to install and use.

SUMMARY

According to one aspect, a circular stapling device includes a handle assembly, an elongate body that extends from the handle assembly, a cartridge assembly mounted on a distal end of the elongate body, a circular cartridge buttress member, a retaining ring member, and a knife assembly.

The cartridge assembly defines an annular containment groove and includes a housing, a pusher member, and a fastener cartridge body. In embodiments, the housing and the fastener cartridge body together define the containment groove therebetween. The pusher member is supported within the housing and is movable between a first position and a second position. The fastener cartridge body is supported on the housing and has a tissue engaging surface that extends to an annular edge.

The circular cartridge buttress member has a body portion and an extension portion. The body portion is supported on the tissue engaging surface of the fastener cartridge body. The extension portion extends from the body portion and over the annular edge of the tissue engaging surface.

The retaining ring member is secured within the containment groove over the extension portion of the circular cartridge buttress member to releasably secure the circular cartridge buttress member to the fastener cartridge body. In embodiments, the retaining ring member is an o-ring. The o-ring is formed of an elastomeric material.

The knife assembly includes a primary knife blade and a secondary knife blade. The primary knife blade is dimensioned to cut tissue. The secondary knife blade is connected to the pusher member. The secondary knife blade is movable with the pusher member to cut the retaining ring member and relieve a tension that the retaining ring member exerts on the extension portion of the circular cartridge buttress member. The tension is sufficient to maintain the circular cartridge buttress member secured to the fastener cartridge body.

The fastener cartridge body supports a stop member that defines a receiving channel dimensioned to receive the retaining ring member and a knife slot dimensioned to receive a distal end portion of the secondary knife blade. The stop member includes a cross member dimensioned to prevent tissue from extruding in front of the distal end portion of the secondary knife blade. The distal end portion of the secondary knife blade is engageable with the cross member upon a translation of the distal end portion of the secondary knife blade through the knife slot. In embodiments, the stop member is formed of a polyethylene material.

The housing includes one or more containment tabs that extends distally from a distal end portion of the housing so that an inner surface of the one or more containment tabs are engageable with an outer surface of the retaining ring member to maintain the retaining ring member secured to the housing after the retaining ring member is cut with the secondary knife blade.

In accordance with another aspect, a cartridge assembly includes a housing, a pusher member, a fastener cartridge body, a circular cartridge buttress member, and a retaining ring member. The cartridge assembly further includes a tissue cutting knife blade dimensioned to cut tissue.

The pusher member is supported within the housing and is movable between a first position and a second position.

The fastener cartridge body is supported on the housing and has a tissue engaging surface that extends to an annular edge. One or both of the housing and the fastener cartridge body define an annular containment groove.

The circular cartridge buttress member has a body portion and an extension portion. The body portion is supported on the tissue engaging surface of the fastener cartridge body. The extension portion extends from the body portion and over the annular edge of the tissue engaging surface.

The retaining ring member is secured within the containment groove to releasably secure the extension portion of the circular cartridge buttress member to the cartridge assembly. In embodiments, the retaining ring member is an o-ring formed of elastomeric material.

A knife blade is connected to the pusher member. The knife blade is movable with the pusher member to cut the retaining ring member and relieve a tension that the retaining ring member exerts on the extension portion of the circular cartridge buttress member. The tension is sufficient to maintain the circular cartridge buttress member secured to the fastener cartridge body.

The fastener cartridge body supports a stop member that defines a receiving channel dimensioned to receive the retaining ring member and a knife slot dimensioned to receive a distal end portion of the knife blade. The stop member includes a cross member dimensioned to prevent tissue from extruding in front of the distal end portion of the knife blade. The distal end portion of the knife blade is engageable with the cross member upon a translation of the distal end portion of the knife blade through the knife slot. In embodiments, the stop member is formed of a polyethylene material.

The housing includes one or more containment tabs that extend distally from a distal end portion of the housing so that an inner surface of the one or more containment tabs are engageable with an outer surface of the retaining ring member to maintain the retaining ring member secured to the housing.

According to yet another aspect, the present disclosure is directed to a method for releasing a cartridge buttress member from a cartridge assembly of a circular stapling device. The method involves providing a circular stapling device including an elongate member having a cartridge assembly mounted on a distal end of the elongate body. The cartridge assembly defines a containment groove and includes a retaining ring member and a cartridge buttress member. The cartridge buttress member has a body portion and an extension portion. The retaining ring member is disposed within the containment groove over the extension portion to secure the body portion on a tissue engaging surface of the cartridge assembly. The method includes cutting the retaining ring member to release the cartridge buttress member from the circular stapling device.

When the circular stapling device includes a knife blade secured to a pusher member supported within the cartridge assembly, the method involves the step of moving the knife blade by moving the pusher member such that the knife blade cuts the retaining ring member. One step includes preventing tissue from extruding in front of the knife blade. One step involves relieving a tension that the retaining ring member exerts on the extension portion of the circular cartridge buttress member. The method includes cutting tissue with another knife blade.

Other aspects, features, and advantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with a general description of the disclosure given above and the detailed description given below, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a perspective view of a circular surgical stapling device according to the present disclosure;

FIG. 2 is an enlarged perspective view of a cartridge assembly of the circular stapling device of FIG. 1;

FIG. 3A is a perspective view, with parts separated, of the cartridge assembly shown in FIG. 2;

FIG. 3B is an enlarged perspective view of a stop member of the cartridge assembly of FIGS. 2 and 3A;

FIG. 4 is an enlarged, longitudinal, cross-sectional view of the cartridge assembly of FIGS. 2 and 3A shown in a first configuration;

FIG. 5A is an enlarged, longitudinal, cross-sectional view of the cartridge assembly of FIGS. 2 and 3A shown in a second configuration with a distal portion of a knife of the presently disclosed circular surgical stapling device shown being distally advanced through the cartridge assembly; and

FIG. 5B is an enlarged view of the indicated area of detail shown in FIG. 5A.

DETAILED DESCRIPTION

As used herein, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Particular embodiments of the present disclosure will be described herein with reference to the accompanying drawings. As shown in the drawings and as described throughout the following description, and as is traditional when referring to relative positioning on an object, the term “proximal” refers to the end of the device that is closer to the clinician and the term “distal” refers to the end of the device that is farther from the clinician. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

Referring initially to FIG. 1, a circular surgical stapling device for use with a buttress material is disclosed herein and is generally designated as 10. In embodiments, the surgical stapling device 10 is adapted for reuse and in certain embodiments; the surgical stapling device 10 is adapted for a single use and can be disposable.

Reference may be made to U.S. Pat. No. 5,915,616 to Viola et al. and commonly owned U.S. Patent Application Publication No. 2011/0174099, filed on Nov. 15, 2010, entitled “Adapters for Use Between Surgical Handle Assembly and Surgical End Effector,” the entire contents of which are incorporated herein by reference, for a detailed discussion of the construction and operation of exemplary circular stapling devices.

The surgical stapling device 10 includes a handle assembly 20, a tubular elongate body 30, an end effector 40, and a knife assembly 50. The handle assembly 20 includes a rotatable advancing member 22 and a pivotable trigger member 24 that are operatively coupled to one or more drivers supported by the surgical stapling device 10. The elongate body 30 extends distally from a distal end portion of the handle assembly 20 to a proximal end portion of the end effector 40 so that the elongate body 30 is disposed between the handle assembly 20 and the end effector 40. In some embodiments, the elongate body 30 has a linear shape along the length of the elongate body 30, and in certain embodiments, the elongate body 30 has a curved shape along the length of the elongate body 30.

The end effector 40 includes a fastener cartridge assembly 100 and an anvil assembly 200. Notably, the fastener cartridge assembly 100 and/or the anvil assembly 200 may be replaced and the circular stapling device 10 may be reused.

With reference to FIG. 5A, the knife assembly 50 is supported within the end effector 40 and includes a substantially cylindrical knife blade 52 adapted to sever tissue and a secondary knife blade 170 adapted to severe a retaining ring member 140 that secures a cartridge buttress member 130 to a cartridge body 120 of the cartridge assembly 100, as will be described in greater detail below. In embodiments, the retaining ring member 140 is an o-ring, a tie, a band, or a suture. In embodiments, the retaining ring member 140 is formed of an elastomeric material.

The circular stapling device 10 can include any number of drivers to effectuate a firing of the stapling device 10 including, for example, a first driver that is operable to effectuate the firing and formation of fasteners 60 (see FIGS. 4 and 5) supported by the end effector 40 and/or the severance of the retaining ring member 140, and second driver that is operable to advance the cylindrical knife blade 52 separate and/or independent of the first driver. Alternatively, a single driver may be used to fire and form the fasteners 60, and to advance one or both the cylindrical knife blade 52 and the secondary knife blade 170.

Turning now to FIGS. 2-5B, the fastener cartridge assembly 100 is mounted on a distal end portion of the elongate body 30. The fastener cartridge assembly 100 includes a housing 110, a fastener cartridge body 120, a circular cartridge buttress member 130, a retaining ring member 140, a stop member 150, a pusher member 160, and a secondary knife blade 170.

With reference to FIG. 3A, the housing 110 includes a shell body 112 having a plurality of fingers 114 extending around a distal end portion of the shell body 112. At least some of the plurality of fingers 114 define an opening 114 a therethrough, and at least some of the plurality of fingers include a containment tab 114 b that extends distally from a distal end portion of the respective fingers 114. The containment tabs 114 b are dimensioned to maintain the retaining ring member 140 secured to the housing 110 after the retaining ring member 140 is cut by the secondary knife blade 170, as described in greater detail below.

With reference to FIG. 4, a radial or annular containment groove 118 is defined between a proximal surface of the fastener cartridge body 120 and a distal end portion of the shell body 112 such that the housing 110 and the fastener cartridge body 120 together define the annular containment groove 118 therebetween. The containment groove 118 extends radially along an inner surface of each containment tab 114 b and is dimensioned to receive the retaining ring member 140.

The containment groove 118 is defined by a chamfer extending radially around the periphery of a distal-most rim or edge of the shell body 112. Each finger 114 is defined by a pair of longitudinally extending elongate slots 116 that are defined in a distal end portion of the shell body 112.

The distal end portion of the housing 110 is dimensioned to receive the cartridge body 120 therein.

The cartridge body 120 is supported on the housing 110 and includes a tissue engaging surface 122 that extends to an annular edge 122 a and defines a plurality of fastener retaining slots 124 in an annular and/or concentric array about the tissue engaging surface 122. Each fastener retaining slot 124 is dimensioned to support a fastener 60 (FIG. 4) such as a surgical staple. The cartridge body 120 includes a sidewall 126 having a plurality of radially spaced detents 126 a extending radially outward from an outer surface of the sidewall 126. Each detent 126 a is dimensioned to be received within one of the plurality of openings 114 a defined in the fingers 114 of the housing 110 to secure the cartridge body 120 to the distal end portion of the housing 110 when the cartridge body 120 is positioned in the distal end portion of the housing 110. A stop member support 128 radially extends from the outer surface of the sidewall 126. Stop member support 128 is dimensioned to secure the stop member 150 to the cartridge body 120.

The cartridge buttress member 130 has a body portion 132 and an extension portion 134 that extends from the body portion 132 of the cartridge buttress member 130. In use, the body portion 132 is supported on the tissue engaging surface 122 of the cartridge body 120. Also in use, the extension portion 134 is dimensioned to extend over the annular edge 122 a of the tissue engaging surface 122 of the cartridge body 120 and against an outer surface of the housing 110.

As seen in FIG. 2, with extension portion 134 of cartridge buttress member 130 extending against the outer surface of the housing 110, the retaining ring member 140 may be positioned around the outer surface of the extension portion 134, along the inner surface of the containment tabs 114 b of the housing 110, and within the radial containment groove 118 to secure the extension portion 134 of the cartridge buttress member 130 to the cartridge assembly 100. In so doing, the retaining ring member 140, together with the containment tabs 114 b and the grooves 118 of the housing 110 function to maintain the body portion 132 of the cartridge buttress member 130 against the tissue engaging surface 122 of the cartridge body 120, as illustrated in FIG. 2.

The retaining ring member 140 is secured within the containment groove 118 over the extension portion 134 to releasably secure the circular cartridge buttress member 130 to the fastener cartridge body 120.

The stop member 150 is securable to the cartridge body 120 and is dimensioned to be received by the stop member support 128 of the cartridge body 120. In embodiments, the stop member 150 is formed of a polyethylene material. As seen in FIG. 3B, the stop member 150 includes stop member body 152 that defines a ring receiving channel 154 therethrough. The ring receiving channel 154 is dimensioned to receive the retaining ring member 140 and secure the retaining ring member 140 within the ring receiving channel 154. The stop member body 152 defines a knife slot 156 dimensioned to receive a distal end portion of the secondary knife blade 170 and a cross member 158 dimensioned to limit distal advancement of the secondary knife blade 170 and prevent tissue from extruding in front or distal of the secondary knife blade 170, as will be described in greater detail below. The knife slot 156 is defined in the stop member body 152 in a direction substantially traverse to the ring receiving channel 154.

The pusher member 160 includes a substantially cylindrical body 162 having a plurality of distally extending pushers 162 a. The plurality of pushers 162 is disposed in an annular and/or concentric array about the cylindrical body 162 of the pusher member 160. The pusher member 160 defines a knife supporting slot 162 b dimensioned to receive a support arm 174 of secondary knife blade 170 to secure the secondary knife blade 170 to the cylindrical body 162 of the pusher member 160. As seen in FIGS. 4 and 5A, a pair of opposed nubs 164 extend from the cylindrical body 162 into the knife supporting slot 162 b. An inner surface of the cylindrical body 162 defines a central opening 162 c dimensioned to receive the cylindrical knife 52 therethrough (see FIG. 5A).

The pusher member 160 is movably supported within the housing 110 and is operatively coupled to a driver adapted to drive the pusher member 160 through the housing 110 between a proximal position and a distal position to dispense the fasteners 60 retained in the fastener retaining slots 124 of the cartridge body 120 and to distally drive the secondary knife blade 170 to severe the retaining ring member 140 upon a firing of the circular stapling device 10.

The secondary knife blade 170 is connected to the pusher member 160 and movable with the pusher member 160 to cut the retaining ring member 140 and relieve a tension that the retaining ring member 140 exerts on the extension portion 134 of the cartridge buttress member 130, the tension being sufficient to maintain the cartridge buttress member 130 secured to the cartridge body 120. The secondary knife blade 170 includes a knife body 172 that is substantially L-shaped. The knife body 172 has blade 176 on a distal end portion thereof and a support arm 174 on a proximal end portion thereof. The support arm 174 extends laterally from the proximal end portion of the knife body 172 and defines a pair of opposed recesses 174 a dimensioned to receive the pair of opposed nubs 164 (see FIGS. 4 and 5A) of the pusher member 160 to facilitate securement of the support arm 174 within the knife supporting slot 162 b of the pusher member 160.

During operation of the surgical stapling device 10, the anvil assembly 200 and the cartridge assembly 100 are approximated by the actuation of advancing member 22 until the anvil assembly 200 and the cartridge assembly 100 are suitably clamped against tissue of a patient. The trigger member 24 is then actuated to fire the surgical stapling device 10. Reference may be made to U.S. Pat. No. 5,915,616 to Viola et al. and U.S. Patent Application Publication No. 2011/0174099 referred to above for a detailed description of the use of a surgical stapling device 10 in a surgical procedure.

With reference again to FIGS. 4 and 5A, upon a firing of the surgical stapling device 10, the pusher member 160 is distally advanced from the proximal position (FIG. 4) to the distal position (FIG. 5A) which drives the pushers 162 a of the pusher member 160 through the fastener retaining slots 124 of the cartridge body 120 into engagement with the fasteners 60 to dispense the fasteners 60 from the fastener retaining slots 124.

The distal movement of the pusher member 160 drives the secondary knife blade 170 distally to severe the retaining ring member 140. Notably, with reference to FIG. 5B, to sever the retaining ring member 140, the secondary knife blade 170 advances distally through knife slot 156 of the stop member 150 and into engagement with a proximal surface of the cross member 158 of the stop member 150 which prevents further distal advancement of the secondary knife blade 170 after the blade 176 of the secondary knife blade 170 cuts through the retaining ring member 140. A distal surface of the stop member 150 including the cross member 158 prevents tissue from extruding in front of the secondary knife blade 170 when tissue is clamped between the anvil assembly 200 and the cartridge assembly 100 upon approximation of the anvil assembly 200 and the cartridge assembly 100.

Upon a severing of the retaining ring member 140, the securement tension imparted to the extension portion 134 of the cartridge buttress member 130 by the retaining ring member 140, prior to a severance of the retaining ring member 140, to secure the cartridge buttress member 130 to the cartridge assembly 100, is released. When the imparted tension is released, the extension portion 134 is freed so that when the device 10 is withdrawn from the surgical site, the cartridge buttress member 130 remains with the stapled tissue and is separated from cartridge body 120.

When the fasteners 60 are dispensed from the fastener retaining slots 124, the legs of the fasteners 60 are advanced through the clamped tissue and any buttress material clamped against tissue including the cartridge buttress member 130 and any buttress material that may supported on the anvil assembly. As the fasteners 60 are distally advanced, the legs of the fasteners are formed by fastener forming pockets defined in an anvil plate of the anvil assembly 200 to secure the buttress material including the cartridge buttress member 130 to the tissue.

Simultaneously or thereafter, the knife 52 is driven distally to sever the clamped tissue so that the buttress material is secured to tissue independent of the circular stapling apparatus 10.

Persons skilled in the art will understand that the structures and methods specifically described herein and illustrated in the accompanying figures are non-limiting exemplary embodiments, and that the description, disclosure, and figures should be construed merely as exemplary of particular embodiments. It is to be understood, therefore, that the present disclosure is not limited to the precise embodiments described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure. Additionally, it is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure, and that such modifications and variations are also intended to be included within the scope of the present disclosure. Indeed, any combination of any of the presently disclosed elements and features is within the scope of the present disclosure. Accordingly, the subject matter of the present disclosure is not to be limited by what has been particularly shown and described. 

1. (canceled)
 2. A cartridge assembly for a circular stapling device, comprising: a circular knife for cutting tissue; a secondary knife; a fastener cartridge body having a tissue engaging surface that extends to an annular edge; a circular cartridge buttress member having a body portion supported on the tissue engaging surface of the fastener cartridge body with a portion of the buttress member extending over the annular edge of the tissue engaging surface; and an elastomeric retaining member releasably securing the buttress member to the tissue engaging surface of the fastener cartridge body, the secondary knife being movable to release the retaining member.
 3. The cartridge assembly according to claim 2, wherein a groove extends around the fastener cartridge body to support the retaining member.
 4. The cartridge assembly according to claim 2, further comprising a stop member positioned to receive the secondary knife blade.
 5. The cartridge assembly according to claim 4, wherein the stop member includes a cross member, the secondary knife blade being engageable with the cross member.
 6. The cartridge assembly of claim 4, wherein the stop member defines a receiving channel for supporting the retaining member.
 7. The cartridge assembly of claim 6, wherein the stop member defines a knife slot disposed transverse to the receiving channel and positioned to receive a distal end portion of the secondary knife.
 8. The cartridge assembly of claim 4, wherein the stop member includes polyethylene material.
 9. A circular stapling device, comprising: an elongate body; a cartridge assembly mounted on the elongate body, the cartridge assembly including: a pusher member movable between a first position and a second position; and a fastener cartridge body having a tissue engaging surface that extends to an annular edge; a circular cartridge buttress member having a body portion and an extension portion, the body portion being supported on the tissue engaging surface of the fastener cartridge body, the extension portion extending from the body portion and over the annular edge of the tissue engaging surface; and a retaining ring member positioned adjacent to the extension portion of the circular cartridge buttress member to releasably secure the circular cartridge buttress member to the fastener cartridge body.
 10. The circular stapling apparatus of claim 9, further comprising a knife assembly, the knife assembly including a primary knife blade and a secondary knife blade, the primary knife blade configured to cut tissue, the secondary knife blade being connected to the pusher member, the secondary knife blade being movable with the pusher member to engage the retaining ring member.
 11. The circular stapling apparatus of claim 10, wherein the secondary knife blade is configured to cut the retaining ring member in response to distal translation of the secondary knife blade relative to the retaining ring member.
 12. The circular stapling apparatus of claim 11, wherein the cartridge assembly includes at least one containment tab that is engageable with the retaining ring member to maintain the retaining ring member secured to the cartridge assembly after the retaining ring member is cut with the secondary knife blade.
 13. The circular stapling apparatus of claim 9, wherein the fastener cartridge body supports a stop member that defines a receiving channel configured to receive the retaining ring member.
 14. The circular stapling apparatus of claim 13, wherein the stop member defines a knife slot configured to receive the secondary knife blade.
 15. The circular stapling apparatus of claim 14, wherein the stop member includes a cross member configured to prevent tissue from extruding in front of the secondary knife blade, the secondary knife blade being engageable with the cross member upon a translation of the secondary knife blade through the knife slot.
 16. The circular stapling apparatus of claim 9, wherein the retaining ring member includes elastomeric material.
 17. A cartridge assembly, comprising: a fastener cartridge body having a tissue engaging surface that extends to an edge; a cartridge buttress member having a body portion and an extension portion, the body portion being supported on the tissue engaging surface of the fastener cartridge body, the extension portion extending from the body portion and over the edge of the tissue engaging surface; and a retaining ring member positioned on the fastener cartridge body to releasably secure the extension portion of the cartridge buttress member to the cartridge assembly.
 18. The cartridge assembly of claim 17, further comprising a knife assembly that is movable relative to the retaining ring member to cut the retaining ring member.
 19. The cartridge assembly of claim 18, wherein the knife assembly includes a first knife and a second knife, the first knife positioned to cut tissue, the second knife positioned to cut the retaining ring member, wherein at least one of the first or second knives is coupled to a pusher member for movement with the pusher member relative to the fastener cartridge body.
 20. The cartridge assembly of claim 17, wherein the retaining ring member includes elastomeric material.
 21. The cartridge assembly of claim 17, wherein the edge of the fastener cartridge body is annular and the cartridge buttress member is circular. 